Navigational light system

ABSTRACT

A flashing light timer for a navigational light having provision to send, receive and utilize a synchronizing signal in which a plurality of lights have their timers connected together so as to flash simultaneously, but will still operate in the event any one of the navigational lights fail. A coded timer for controlling the flashing code of a navigational light having a plurality of time constant circuits connected to a counter for readily changing the flashing code of a light. A navigational light having a logical circuit for sensing a burned out lamp without requiring a resistive element. A lamp changing circuit that allows the new lamp to be placed accurately into operative position. And a circuit for switching off power from the navigational light during the lamp changing process for preventing sparking of the electrical contacts.

United States Patent [191 [111 3,

Jacobs 1 1 Dec. 17, 1974 NAVIGATIONAL LIGHT SYSTEM Primary ExaminerJohnW. Caldwell Assistant Examiner-Daniel Myer [75] Thomas A. Jacobs HoustonAttorney, Agent, or Firm.lefferson D. Giller; James [73] Assignee:Tideland Signal Corporation, F, Weiler; William A. Stout Houston, Tex.

[22] Filed: Jan. 4, 1973 [57] ABSTRACT [21] Appl. No.: 320,982 Aflashing light timer for a navigational light having provision to send,receive and utilize a synchronizing Related Application Data signal inwhich a plurality of lights have their timers [62] Division of Ser. No.211,605, Dec. 23, 1971, Pat. No.

connected together so as to flash simultaneously, but

will still operate in the event any one of the navigational lights fail.A coded timer for controlling the 340lii5olb3gjflig flashing code of anavigational light having a plurality of time-constant circuitsconnected to a counter for [58] Field of Search 340/251, 29; h h n d f hA I 315/8833. 240/37 1 rea iyc angingt e as in g co co a ig t.navigational light having a logical circuit for sensing a burned outlamp without requiring a resistive element. [56] References Clted A lampchanging circuit that allows the new lamp to UNITED STATES PATENTS beplaced accurately into operative position. And a 2.258.575 10/1941MacKay 240/371 circuit for switching off power from the navigational21343-085 2944 v i light during the lamp changing process for preventing2,465,795 3/1949 Foulds 315/89 Sparking of the electrical contacts3.571135 5/1971 Steen i 315/93 4 Claims, 8 Drawing Figures 22a 22b 22c22d 229 221 F ii a ii ii i '4 I8 20 W 2 I DAYLIGHT i CONTROL LAMP I lCONTROL u TIMER SYNCHRONIZ- [N6 LAMP OUT I TERMINAL DETECTOR I END OFM30 SEARCH J l C ONTR fig 26 T l'i'tilllz PAIENT um: I "(I874 sum 2 o 5PATENTEB 1 71974 85 587 sum 3 [3 5 NAVIGATIONAL LIGHT SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS This application is a divisionof application Ser. No. 211,605, filed Dec. 23, 1971, now U.S. Pat. No.3,781,853, issued Dec. 25, 1973.

BACKGROUND OF THE INVENTION It has been conventional to flash insynchronism multi-light installations for navigational lights, such aslights for marking buoys, channels and obstructions, using the so-calledmaster-slave system. In this system only the master light contains atimer and an automatic sun switch and the power switch that turns themaster light and all of the slave lights off and on. In the event thetotal current required by the slave lights is more than the power switchof the master light can handle, a third type of light, the slaverepeater, is required. The slave and slave repeater lights have noautomatic sun switch or timer and only the repeater has a power switchto take some of the current load from the master. Failure of the masterlight means failure of all of the lights of the navigational system andthree different types of lights may be required for a multi-lightinstallation. Also in the past, timers were designed to flash complexcodes, that is a characteristic consisting of more than just an on-offflash as a Morse code letter, using a series of flip-flops to achievethe proper code such as U.S. Pat. No. 3,027,491. For example in a lightflash characteristic equivalent to dot, dot, dash, the two dots would bethe basic time, and also the dash time must be a multiple of the dottime. There is no way to adjust the individual times separately and theflip-flop timer approach offers very little versatility. Additionally,once a timer has been designed to flash one code sequence, it cannotrealistically be made to flash another and thus the flip-flop methodrequired that a timer be designed for each different characteristic.

It has also been standard practice to sense a burned out lamp conditionby monitoring the current through the lamp. One method requires the useof a resistive device in series with the light. Such a device requirespower which could be used by the light which was disadvantageous,particularly in navigational lights which commonly use battery power.

It is further conventional in lamp changing systems to rotate a turretcontaining a plurality of spare lamps such as shown in U.S. Pat. No.3,308,358, but no provision is made to insure that the turret motorstops in the same place every time which is important in a precisionoptical navigational lantern. Furthermore, the rotation of a turret mayproduce electrical sparking at the electrical contacts which isundesirable, particularly in hazardous electrical locations.

The present invention is directed to an improved navigational lightsystem which overcomes the difficulties of the prior art.

SUMMARY One feature of the present invention is the provision ofaplurality of navigational lights each including a separate flashingtimer in which the timer of each light is connected to the input of theflashing timer of all of the lights whereby all of the timers areactuated when one of the timers is first actuated thereby synchronizingall of the navigational lights, but insuring that in the event one ofthe lights fails that the remainder will operate and will operate insynchronism.

Another feature of the present invention is the provision of anavigational light having a versatile timer which has the capability totime a light to flash any code, such as a letter or any number from oneto ten of the international Morse code. The present timer utilizes aplurality of different time constant circuits con nected to the timer,and a counter having a plurality of sequentially actuated outputs. Theoutputs of the counter are connected to selected of the time constantcircuits through a code board to provide the desired flashing code andcan be easily varied to change the code if desired.

Another object of the present invention is to provide a circuit forsensing a burned out lamp without using a power consuming resistiveelement in series with the lamp.

Still a further object of the present invention is the provision of alamp changing circuit in which the motor is actuated by a reverse pulseafter a new lamp is rotated into position to allow the turret to beaccurately aligned so that the new lamp will be in a proper position inline with the optic of the lantern.

Yet a still further object of the present invention is the provision ofswitching off power from the electrical lamp contacts during the lampchanging process in order to enable the lamp to be non-sparking so as tobe used in hazardous electrical locations.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram in schematicof a single navigational light of the present invention,

FIG. 2 is an electrical schematic of one type of timer that may be usedto provide a standard on-off flash characteristic and may besynchronized with other lights in an installation,

FIG. 3 is an electrical schematic of a timer that may be used to flash alight in various combinations of short and long flashes,

FIG. 4 is an electrical schematic of a lamp-out sensing circuit and lampchanging circuit,

FIG. 5 is an elevational view, partly in cross section of a lampchanging turret,

FIG. 6 is a cross-sectional view taken along the line 66 of FIG. 5,

FIG. 7 is a cross-sectional view taken along the line 77 of FIG. 6, and

FIG. 8 is an enlarged cross-sectional view of the turret and power brushillustrating the alignment of the turret after changing a lamp.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, asingle navigational light is shown generally referred to by thereference numeral 10. The light 10 generally includes a power sourcesuch as a battery 12, a timer 14 which is continuously cycling and whichincludes a synchronizing terminal 16, which will be more fully describedhereinafter, a suitable sun switch or daylight control circuit 18, whichmay be of any suitable type, suchas shown in U.S. Pat. No. 3,492,529. Ifthe ambient light level is above a preset level, the timer signal isstopped by the daylight control unit 18. Ifthe ambient light is below adesired level, the timer signal is coupled to a lamp control circuit 20to provide voltage and current amplification of the timer signal to oneof a plurality of lamps 22a-22f, one of which is in the operativeposition in a lamp lens, here shown as number 22b. A lamp-out detectorcircuit 24 determines when the lamp in the operative position is burnedout and in that event actuates a motor control circuit 26 to drive amotor 28 to turn a lamp turret to move one of the spare lamps into theoperative position. Actuation of the motor control circuit interruptsthe timer signal and also energizes the end of search circuit 30 and inthe event all of the lamps 22a-22f are burned out and the motor controlcircuit 26 is not turned off, the end of search circuit 30 will run outand turn off the power circuit to save power of the battery 12.

One of the features of the present invention is the provision in anavigational light system having a plurality of navigational lights eachof which includes a timer 14 and in which each of the outputs of all ofthe timers 14 are connected to the synchronizing terminal 16 of all ofthe timers 14 whereby the timers 14 of all of the navigational lights 10will be synchronized in order that all of the lights 10 will flash atthe smae time. That is, the timer 14 will function normally to start itsown sequence to originate a synchronizing pulse but if a synchronizingsignal appears on the synchronizing terminal 16 before the timer 14 isready to create its own on" signal, the synchronizing signal willinitiate all of the timers 14. Thus the timers 14 will follow theleader.

Referring now to FIG. 2, the timer 14 may be a standard unijunctiontimer consisting of resistors 31, 32, 33 and 34; capacitor 35; diode 36;and unijunction transis tor 37. The pulse output of the unijunctiontimer is amplified by transistors 38 and coupled through diode 39 to aconventional monostable multivibrator 40, as is conventional. When themultivibrator 40 is in the stable state, voltage from the battery 10 andregulator and filter 13 is present at the top of resistor 31. Capacitor35 then charges up through resistor 31 and variable resistor 32. Thischarge time corresponds to the off time. Unijunction 37 fires and anegative pulse is generated between resistor 34 and diode 36. This pulseis coupled by capacitor 41 to transistor 38 where the pulse is invertedand amplified. The pulse (now positive) is coupled through diode 39 tomonostable multivibrator 40 which is now triggered to the astable state.in the astabl'e state there is no voltage on resistor 31 so the timer isinactive. At the same time, the output of the astable state of themultivibrator 40 which is connected to the base of transistor 42 ishigh. This high at the base and emitter of transistor 42 is the on timepulse for the lamp timer and is connected to the lamp control circuitthrough terminal 44. At the end of the time constant of the astablestate, the multivibrator 40 flops back to the stable state, the signalto transistor 42 goes to zero and the cycle is repeated.

is is also noted from FlG. 2, that the timer signal on the emitter oftransistor 42 is coupled through resistor 43 to transistor 44. At thecollector of transistor 44 the signal is inverted and amplified, andcoupled. through resistor 45 to the synchronizing terminal 16. lt can beseen now that the synchronizing terminal 16 is high during the off timeand low during the on time. Further from FIG. 2, it can be seen that thesignal at the synchronizing terminal 16 is coupled through resistor 46to the base of transistor 47. Capacitor 48 and resistor 46 act as afilter to keep noise spikes from turning on transistor 47. Diodes 49 and50 are added to increase the required turn on signal and thus aid innoise immunity. The signal is then inverted on the collector oftransistor 47 and coupled through resistor 51 to transistor 52 where itis amplified and inverted. Thus, the collector of transistor 52 is inphase with the signal on the synchronizing terminal 16. Therefore, whenthe timer is switched to the on state, the collector of transistor 52changes from a high" to a low of nearly zero voltage. The transitionfrom high to low of the collector of transistor 52 causes a negativespike to be coupled through capacitor 53 to the unijunction timerbetween base two of the unijunction transistor 37 and diode 36. Becauseof this, the base two voltage of the unijunction transistor 37 isbrought below the emitter voltage forcing the unijunction 37 to tire. Ifthe timer 14 is being operated as a single unit, the negative spikethrough capacitor 53 has no effect since the unijunction 37 has alreadyfired (it was the firing of the unijunction 37 that created thisnegative spike). However, when more than one timer 14 have theirsynchronizing terminals 16 connected together, the first timer 14 toflash causes a low to be seen at the common synchronizing terminal 16.This low results in the negative spike through capacitor 53 in theremaining timers 14 causing them to switch to the on position. Theresult of this is that all of the timers 14 connected together come onat the same time once the on time has been initiated by the firstactuated timer 14. Once the on time has been initiated, each flasherfollows its own on and off time constant until the first flasher turnson again. Then once again all of the flashers 14 will follow the leaderand the cycle repeats itself again.

The timer shown in FIG. 2 gives a simple on and off flashing code. Amore versatile and complex code may be provided by the timer of FIG. 3which has the capability to time a light to flash in a variable codesuch as a letter or number from one to ten of the international Morsecode and which can be easily and inexpensively adjusted to change to adifferent code. The unijunction timer of FIG. 3 consists of resistors 56through 65; diodes 66 through capacitors 71 through 73 and complementaryunijunction transistor 74. A plurality of separate RC time constantpaths, here shown as four, may be provided for the unijunctiontransistor 74. The diodes 66 through 70 isolate the four different RCtime constant paths from each other. The first path, which may be usedfor a short time pulse, consists of resistors 58 and 59, diode 70 andcapacitor 73. The second path,

which may also be used for a short pulse, consists of resistors 60 and61, diode Y69 and capacitor 73. The third path which may be used for alonger time period or pulse, consists of resistors 62 and 63, diodes 67and 68, and capacitors 72 and 73. The fourth time constant path whichmay be used for an even longer time period or pulse, consists ofresistors 64 and 6S, diodes 66 and 67, and capacitors 71, 72 and 73. Theconnection of these various time constant paths to an appropriate signalsource will be described hereinafter. The output is taken from base oneof the complementary unijunction 74 and is coupled through a capacitor75 to a transistor 76. At the collector of transistor 76 the pulse fromthe unijunction 74 is amplified, inverted, and fed into the clock inputterminal 81 of a decade counter, generally indicated by the referencenumeral 80. The counter is a conventional counter such as RCA Model No.CD4017AE and produces ten distinct and separate sequential andseparately timed output signals called out as counts through 9. Uponreceiving a pulse at the clock input 81, the output from the counter 80shifts to the next numeral order count terminal in sequence. Theterminal for the count being sampled is high while all other countterminals are low. The counts 0 through 9 from the counter 80 are diodecoupled to terminals 90-99 on a code board 100.

The code board 100, in addition to the terminals 90-99 for the separatecount outputs from the counter 80, has a signal out terminal 105 andfour terminals that, after going through an amplifier board 106 connectto the four RC time constant paths previously described. Therefore, byproperly interconnecting the wiring on the code board 100 between thecount terminals 90-99, the time constant feedback terminals 101 through104, and the output terminal 105 will determine the combination of longand short light pulses the timer will produce. As an example only, theconnections will be described in which the navigational light isrequired to flash a Morse letter F in which the dots are half a secondlong, the dashes are two seconds long, the eclipses are one second long,and the duty cycle is twenty seconds. The letter P in Morse code is dot,dash, dash, dot which will be displayed as a half second on, I secondoff, 2 seconds on, 1 second off, 2 seconds on, 1 second off, half secondon, and 12 seconds off. Also assume that the path one time constant pathhas been adjusted a half second long, path 2 to 1 second long, the timeconstant path 3 to 2 seconds long, and the time constant path 4 to 3seconds long. Since the on light pulses will be through terminals 101and 103 to the first and third time constant paths, a jumper connectionwill be provided between the signal out terminal 105 and the terminals101 and 103. Since the code starts with a dot, which is a short time,count 0 from the counter 80 will be connected from terminal 90 to theterminal that is fed back to the one half second time constant pathterminal 101. The next function is the 1 second eclipse so count I fromthe counter 80 is fed from terminal 91 on the code board 100 to terminal102 to the one second time constant path. The next function to beperformed is the two second dash which will be count 2 from the counter80 through terminal 92 which must be connected to terminal 103 which isfed to the path three time constant of two seconds. Count 3 is anotherone second eclipse, so terminal 93 is connected to time constant pathtwo or terminal 102. Count 4, another dash of two seconds duration, isobtained by connecting terminal 94 to path three or terminal 103. Countobtains another one second eclipse by connecting terminal 95 to terminal101. Count 6 is another half second dot and is obtained by connectingterminal 96 to terminal 101 to obtain a half second time constant path.Counts 7, 8 and 9 from the counter 80 may be used together to achievethe twelve second off time, therefore, these three counts may beobtained by connecting each of the terminals 97, 98 and 99 to the foursecond time constant path or terminal 104.

From the above description, it can be seen that various combinations oflong and short times may be easily obtained merely by making therequired connections on the code board 100 between the output terminals90-99 from the counter 80 and the time constant feedback paths throughterminals 101 through 104. Of course, a still more versatile and complexcode can be provided by providing the timer with additional timeconstant paths and a counter with greater number of outputs. However,the use of the decade count with the decoder board and the various timeconstant feedback paths provides a versatility and ease of operation notavailable in the conventitonal flip-flop type counters.

The synchronizing of the timer of FIG. 3 when a plurality of timers 14are used is the same as that for the timer of FIG. 2. The synchronizingsignal is filtered and converted to a pulse which is coupled to base twoof the unijunction transistor 74. The synchronizing signal originates atthe carry out terminal of the decade counter 80. This signal changesfrom a low to a high whenever the count makes a transition from count 9to count 0. Therefore, when the first of a series of timers of FIG. 3 ina string of synchronize timers makes the transition from count 9 tocount 0, a synchronizing pulse is originated and provided at thesynchronization terminal 16 for the other times 14 to synchronize on.The synchronization signal has one function in the timer of FIG. 3 thatdoes not apply to the timer of FIG. 2. In addition to synchronizing theunijunction timer, the synchronizing signal must also reset the decadecounters 80 so that all counters reset by coupling the synchronizingpulse through a small capacitor to the reset terminal 111 of the decadecounter 80. Therefore, after the origin of the first synchronizingpulse, all interconnected timers of the FIG. 3 type will be reset tocount 0 and their unijunction timers will be starting their timingsequence together.

Referring now to FIG. 4, the output from the timer is connected atterminal 44 to a suitable daylight control circuit 18, where it isinhibited during daylight hours and allowed to pass at night and is thenfed to line 116. The timer signal from line 116 is then fed through somecurrent amplification stages to transistor 118 which is the power switchfor the lamp 22b which is in the'operative position in the lens of thenavigational light 10.

Of course, when the lamp 22b which is in the operative position burnsout, it is desirable to sense this fault and actuate a lamp changingcircuit to rotate a new bulb into the operative position. However, it isundesirable to sense the burned out lamp with a resistive element asthis consumes power which can otherwise be used. The present lamp outsensing circuit includes a logic circuit including diodes 120 and 121;capacitor 122, resistors 123 and 124 and transistor 125. Diodes 120 and121 are connected in configuration of a standard or gate. Under normalconditions when the lamp 22b is in the on condition, the anode of diode121 is connected to a high and the anode of diode 120 is connected to alow. During the normal lamp off condition, the anode of diode 120 ishigh and the anode of diode 121 is low. Therefore, at all times duringnormal operating conditions, the anode of at least one of the two diodes120 and 121 is connected to a high and so, due to diode action, there isalways a high present at the junction of the two cathodes and resistors123. During the time that the lamp 22b is off, the anode of diode 120 isconnected to the positive voltage through the filament of the lamp 120.If the lamp 22b were burned out and the filament were open, there wouldbe no path to provide positive voltage for the anode of diode 120. Andsince during the off time the anode of diode 121 is not connected to ahigh, if the lamp 22b is burned out, there is no longer a positivevoltage available at resistors 123 and 124. If the positive voltage isno longer available to transistor 125, the transistor 125 is forced toturn off. When the transistor 125 turns off, the collector of transistor125 goes high. And it is the high on the collector of transistor thatactuates the motor drive circuit.

The motor drive circuit (FIG. 1) forms several major functions. Thiscircuit drives the motor 28 forward to move a new bulb in the operativeposition in the navigational light. When a new lamp is moved intooperational position, the circuit 26 reverses the polarity of thevoltage applied to the motor 28 as will be more fully described. Themotor is driven through a gear train and one-way clutch and even thoughthe motor runs in reverse, it is not allowed to drive the turretbackwards, but a reverse pulse to the motor 28 releases the forwardpressure on the clutch and allows the electrical contact to makeconnection with a recess on the turret and by spring action to push tothe bottom of the recess and cause the turret to achieve a straight upand accurately aligned position. Another major function of the motordrive circuit 26 is to interrupt the timer signal coming from the timer14 during the time that the motor 28 is rotating and changing lampbulbs. This, as will be described, insures that no power is applied tothe turret while the electrical brush contact connections are being madeor broken and thus prevent electrical arcing which may be dangerous,particularly in hazardous locations.

Continuing with a description of FIG. 4, the motor drive signal from thecollector of transistor is coupled through resistor 126 through the baseof transistor 130. Transistor 130 is turned on causing the collector oftransistor 130 to become low. The low on the collector of transistor 130is coupled through a diode 131 to the junction of resistor 132 andcapacitor 133. The negative pulse on the output of capacitor 133 is seenon the base of transistor 134 where it is a reverse bias and does notcause the transistor 134 to turn on. The negative pulse is then passedto ground through diode 135 and resistor 136. The low on the collectorof transistor 130 is also seen at the junction of diode 137 and resistor138 where it is used to perform two functions.

The low coupled through resistor 138 turns on npn transistor 139. Withtransistor 139 in the on state, a high is seen on resistor 140 and zenerdiode 141. The voltage from the junction of resistor 140 and diode 141is transmitted over line 142 through diode 143 to forward biastransistor 144. With transistor 144 turned on, a path is completed toallow current to flow from the positive voltage 145 through transistor144 through the motor 28 in a forward direction, through transistor 146and then to ground. The motor 28 therefore is running in the forwardposition to replace the bulb 22b with a new bulb 220.

The same low at the junction of diode 137 and resistor 138 which causesthe motor 28 to move in the forward direction, is also seen through thediode 137 at the junction of resistors 150 and 151 and capacitors 152.This low is coupled through resistor 150 to forward bias transistor 153.With transistor 153 in the on condition, a high is made available toreverse bias the base-emitter junction of transistor 154 with transistor1S4 held off by transistor 153, the timing signal on line 116 isinhibited and not allowed to turn on the transistor 118 which wouldapply power to the lamp circuit. Thus, it is now seen that when power isapplied to the motor drive circuit, the motor runs in the forwarddirection and the power is removed from the lamp circuit to prevent thepossibility of the electrical contacts areing and causing a spark in ahazardous location.

Of course, when a good lamp, for instance 220, is rotated into position,a high is encountered at the anode of diode 12 0 again and transistor130 is turned off forcing its collector high. The high on the collectorof transistor 130 is seen at the junction of diode 137 and resistor 138.The high is seen through resistor 138 to the base of transistor 139turning off transistor 139 and therefore turning off the voltage thatdrives the motor 28 in the forward direction. At the same time, thepositive voltage at the junction of diode 137 and resistor 138 reversebiases diode 137. With diode 137 reversed biased, positive potential,after the delay of the combination of resistor 151 and capacitor 152, isapplied to the base of transistor 153. The positive on the base oftransistor 153 turns off transistor 153 and the timing signal on line116 is no longer inhibited.

When the collector of transistor 130 goes high, diode 131 becomesreverse biased. With the diode 131 reversed biased, a positive potentialthrough diode and resistor 132 is seen at capacitor 133. This produces apositive spike that turns on transistor 134 for a short time. As long astransistor 134 is turned on, a low is seen through diode 161 thatforward biases transistor 162. This same low is seen through resistor163 to turn on transistor 164. With transistors 162 and 164 turned on,there is a path for current flow from positive voltage line 145 throughtransistor 164, through the motor 28 in the reverse direction andthrough transistor 162 to ground. Thus, it can be seen that when themotor drive is removed, the motor 28 will reverse its direction ofrotation for a short time.

Referring now to FIGS. 5 through 8, a conventional lamp holding turretgenerally indicated by the reference numeral is shown which generallyholds a plurality of lamps, for esample the lamps 220 through 22f ofFIG. 1. Motor 28 drives the turret 170 through a one-way clutch 171.Metal contacts having a recess, preferably in the shape of a V-grovecontact 172a through l72f are provided, one for each of the lamps 22athrough 22f. A spring-loaded electrical brush contact 173 is providedpreferably having a circular or ball point 174 which makes and breaks acontact with the V-grooves 1720 through 172f to complete an electricalcircuit to the bulb which is in the operative position. Thus, when themotor 28 rotates the turret 170 the electrical brush contact 173contacts the proper V- shaped groove to provide power to the lamp in theoperative position. When the lamp out circuit 24 detects a burned outfilament, the motor 28 is energized to drive the turret through theone-way clutch 171 until the brush 173 contacts one of the V-shapedgrooves and the lamp out detector circuit 24 measures a positive voltagethrough the filament of the new lamp now in the operative positionstopping the motor. However, it is important that the turret 170 and thebulb in the operative position is accurately aligned since they areplaced at the focal point of a lens system in a navigational light.Obviously, the width of the Vshaped groove 172a through 172f and thecircular point 174 on the electrical brush 173 must be of a sufficientwidth to provide a good electrical contact. However, the motor 28 mayhave a certain amount of overrun and its electrical actuation anddeactuation may not be sufficiently accurate to correctly align theturret 170 and the operative bulb. Therefore, as previously described,when the motor 28 drives the turret 170 forward and finds a good lamp, areverse polarity of voltage is applied to the motor 28. Even though themotor runs for a short period in reverse, it does not drive the turretbackwards due to the action of the one-way clutch 171. However, thereversal of the motor does release the forward pressure on the clutch.With the pressure on the clutch released, the spring-loaded electricalbrush 170 is sufficient to cause the ball point 170 to move the turret170 a slight distance allowing the ball 174 to seek the apex 175 of theV-shaped groove of the lamp in the operative position thereby accuratelycausing the turret 170 to achieve a straight up position and accuratelyalign the new bulb in the optical lens of the navigational light.

The present invention, therefore, is well adapted to carry out theobjects and attain the ends and advantages mentioned as well as othersinherent therein. While a presently prefered embodiment of the inventionis given for the purpose of disclosure, numerous changes in the detailsof construction and arrangement of parts will readily suggest themselvesto those skilled in the art and which are encompassed within the spiritof the invention and the scope of the appended claims.

What is claimed is:

1. In a navigational light having a power supply, a timer, a lamp-outsensing circuit, a lamp changing circuit having a rotating turret withlamps therein and a power brush which supplies power to contactsconnected to the lamps, the improvement in a lamp changing circuitcomprising,

switching means connected to and actuated by the lamp changing circuit,said switching means connected between the timer output and the powersupply for disabling the timer signal from the lamp when actuated by thelamp changing circuit thereby preventing power from being supplied tothe brush while the lamp changing circuit is rotating the turret therebypreventing electrical arcing between the brush and the contacts.

2. In a navigational light having a lamp changing circuit having arotating turret containing a plurality of lamps and driven by a motor toplace one of the lamps in an operative position in which electricalcontacts connected to the lamps in the turret include a V-shaped recessand power is supplied to the recesses through a spring brush having apoint, the improvement in the lamp changing circuit comprising,

a one-way clutch connected between the motor and the turret forproviding a driving force to the turret in the forward direction butdisconnecting the driving force of the motor from the turret when themotor is reversed,

means connected to the motor for indexing the turret when the lamp inthe operative position is burned out to place a new lamp in theoperativeposition, and

means for providing a reversing pulse to the motor at the end of theindexing movement for relieving all driving forces of the motor as theone-way clutch is reversed thereby allowing the point of the springbrush to seek the center of the V-shaped recess and accurately align theturret and operative lamp.

3. A navigational light having a power supply, a timer, a lamp changingcircuit, a lamp filament circuit having a series connected power supplyand power switch, a rotating turret containing a plurality of lamps anddriven by a motor through a one-way clutch to place one of the lamps inan operative position in which electrical contacts connected to thelamps in the turret include a recess and power is supplied to therecesses through a spring brush comprising,

first switching means for actuating the lamp changing circuit,

a first electrical connection between the timer output and the switchingmeans for supplying a signal to the switching means from the timerpreventing actuation of the lamp changing circuit during the timingsignal,

a second electrical connection connected between the lamp filament andthe power switch for supplying a signal to the switching means when thelamp is unpowered by the timing signal for preventing actuation of theswitching means but causing actuation of the switching means when thefilament is burned out,

said lamp filament circuit having no current sensing resistivecomponents,

second switching means connected to and actuated by the lamp changingcircuit, said second switching means connected between the timer and thepower supply for disabling the timer signal from the lamp when actuatedthereby preventing power from being supplied to the brush while the lampchang ing circuit is rotating the turret thereby preventing electricalarcing between the brush and the contacts.

4. The apparatus of claim 3 including,

means for providing a reversing pulse to the motor at the end of theindexing movement for relieving all driving forces of the motor as theone-way clutch is reversed thereby allowing the spring brush to seek thecenter of the recess and accurately align the turret and new operativelamp.

1. In a navigational light having a power supply, a timer, a lamp-outsensing circuit, a lamp changing circuit having a rotating turret withlamps therein and a power brush which supplies power to contactsconnected to the lamps, the improvement in a lamp changing circuitcomprising, switching means connected to and actuated by the lampchanging circuit, said switching means connected between the timeroutput and the power supply for disabling the timer signal from the lampwhen actuated by the lamp changing circuit thereby preventing power frombeing supplied to the brush while the lamp changing circuit is rotatingthe turret thereby preventing electrical arcing between the brush andthe contacts.
 3. A navigational light having a power supply, a timer, alamp changing circuit, a lamp filament circuit having a series connectedpower supply and power switch, a rotating turret containing a pluralityof lamps and driven by a motor through a one-way clutch to place one ofthe lamps in an operative position in which electrical contactsconnected to the lamps in the turret include a recess and power issupplied to the recesses through a spring brush comprising, firstswitching means for actuating the lamp changing circuit, a firstelectrical connection between the timer output and the switching meansfor supplying a signal to the switching means from the timer preventingactuation of the lamp changing circuit during the timing signal, asecond electrical connection connected between the lamp filament and thepower switch for supplying a signal to the switching means when the lampis unpowered by the timing signal for preventing actuation of theswitching means but causing actuation of the switching means when thefilament is burned out, said lamp filament circuit having no currentsensing resistive components, second switching means connected to andactuated by the lamp changing circuit, said second switching meansconnected between the timer and the power supply for disabling the timersignal from the lamp when actuated thereby preventing power from beingsupplied to the brush while the lamp changing circuit is rotating theturret thereby preventing electrical arcing between the brush and thecontacts.
 4. The apparatus of claim 3 including, means for providing areversing pulse to the motor at the end of the indexing movement forrelieving all driving forces of the motor as the one-way clutch isreversed thereby allowing the spring brush to seek the center of therecess and accurately align the turret and new operative lamp.